The present invention relates to a backlash preventing device for a fishing reel and, more particularly, to a backlash preventing device for preventing a fishline from backlashing by restraining the rotating speed of spool at the commencement of casting from becoming greater than the let-off speed needed by the fishing line.
In the prior art, there exists a backlash preventing device for a fishing reel, as is disclosed in Japanese Utility Model Laid-Open No. 58-13076. This device is constructed such that there is attached integrally and coaxially to a spool a braking cylinder which is made of a non-magnetic conductive material, such that a plurality of magnets are arranged equi-distantly on the inner and outer circumferences of that cylinder and at a desired spacing from the circumferential faces so that a braking torque directed oppositely to the rotating direction of the cylinder is generated in the cylinder by eddy currents which are established when magnetic fluxes of those inner and outer magnets extend through the cylinder thereby to brake a spool to prevent the backlash of the fishline, and such that the braking force to be applied to the spool can be adjusted by changing the relative positions of the inner and outer magnets in the circumferential direction, and such that the adjustment of the braking force is performed by operating a dial which is connected to the frame of the aforementioned inner or outer magnets. Moreover, the setting of the force for braking the spool is performed by making an adjustment to a predetermined scale in advance of the casting in accordance with the kind of hook and bait, the distance to a point, and so on, and the graduations are so set that the rotating speed of the spool immediately after the start of the casting does not overcome the let-off speed of the line, i.e., that the rotating speed is set at the optimum value that will restrain the high-speed rotations of the spool to prevent the backlash of the line.
Here, the braking torque Tc by the aforementioned eddy current brake is given by the following Equation: EQU Tc=k.phi..sup.2 n (1)
(wherein k : a constant: .phi. : a magnetic flux; and n : the rotating speed of the spool).
As a result, the braking torque characteristics during the casting are plotted, as indicated by Curve I of FIG. 7, if the braking force to the spool is so preset as to restrain the high-speed rotations of the spool at the initial stage of casting. On the other hand, it takes about 2 to 3 seconds from the casting initiation for the hook and bait to be cast to a point spaced away about 30 m. However, there occurs about 0.5 seconds immediately after the casting starts sufficiently high speed spool rotation to establish backlash in the line. This line backlash can be prevented if the interim rotating speed is restrained. If the braking force is still set at the value at the stage of casting initiation even after the above-specified lapse time of 0.5 seconds, however, the the spool rotation is restrained more than necessary because the braking torque is proportional to the square of the magnetic flux .phi., as is apparent from the foregoing Equation (1). This results in reduction of the casting distance of the hook and bait. If the casting force is increased so as to increase the distance, on the other hand, the rotating speed of the spool at the starting stage of the casting may invite the backlash in the line. In either event, there arises a problem that the casting distance of the hook and bait are restrained more than necessary. Since the setting of the braking force and the operation of releasing the clutch are conducted independently of each other in the prior art, moreover, another problem is that the casting operation is thereby complicated.
The present invention has been conceived so as to solve the aforementioned problems of the prior art, therefore it is an object of the invention to provide a backlash preventing device for a fishing reel, which is enabled to ensure the backlash prevention of a fishline, to improve the casting distance of hook and bait and to facilitate the casting operation.
In order to realize the above-specified object, the backlash preventing device for a fishing reel comprises: a non-magnetic conductor mounted integrally in a spool; magnets for applying to said non-magnetic conductor magnetic fluxes for generating a braking torque from resulting eddy currents; an adjuster for adjusting the magnetic fluxes of said magnets acting upon said non-magnetic conductor; a setting mechanism for operating said adjustor to arbitrarily adjust the braking force upon said spool; and a knob arranged movably in front of said spool for releasing a clutch between said spool and a line take-up drive mechanism, characterized in that, when said knob is moved farther from a clutch releasing position, said adjustor is made movable in response to the movement of said knob and in association with said clutch.